The present invention relates to a method for simplifying the localization of a subsurface zone studied within the scope of seismic exploration operations. More particularly, the object of the method according to the invention is to simplify the allocation operations through which seismic type data for example are associated with the topographic data of the respective places where the seismic type data have been picked up by receivers.
Seimic prospecting methods generally comprise transmission, into the formations to be explored, of seismic waves in the form of vibrations or impulses, reception of the waves which are propagated in the subsoil by a receiving set comprising a plurality of sensors arranged at the subsoil surface or close to it, recording of the waves picked up and a series of processings for improving the representativeness of the seismic sections achieved from the recordings.
Modern methods sometimes use data acquisition devices distributed at regular intervals over a distance of several kilometers. Each such device is adapted for collecting seismic signals picked up by one or several geophones, and for digitizing and storing the signals in a memory before the real or delayed time transmission thereof to a central control and recording station. The various acquisition devices generally transmit sequentially the collected data to the central station, either directly or by means of relay elements.
Various transmission systems of this type are described for example in the published French patent applications 2,627,652; 2,608,780; 2,602,875; 2,599,533; 2,538,561; 2,511,772.
The seismic sections obtained after seismic operations being representative of a subsurface zone vertical with respect to the alignment of receivers arranged in the field, it is therefore important to locate in space all the reception sites and thus to associate therewith precise topographic data.
Locating the position of the reception points is often achieved upon installing the sensors and the acquisition devices in the field. A well-known technique consists of using for example a radiopositioning system which calculates the position thereof with respect to those of several transmitters whose positions are known, located on the ground or on satellites, as is well-known to those skilled in the art. The position data read on the site of each sensor or at the barycenter of the set of interconnected sensors constituting each seismic receiver are associated for example with the serial number of the acquisition device and/or with the site number thereof in the series of devices distributed in the field. All these data collected by the field crew can be brought to the central station to be recorded there on an auxiliary recorder, which is often different from the recorder intended for the seismic data. The data must therefore necessarily be put in relation on two different supports so as to pair the seismic data with corresponding topographic indications, and this is sometimes a source of errors. Error and confusion risks also increase because of the ever larger number of acquisition devices that are set in the field for seismic exploration, which extends the transfer and pairing operations.
U.S. Pat. No. 4,589,100 describes a well-known seismic exploration system comprising a central control and recording station, a set of seismic acquisition devices distributed in the field in a grid pattern and a positioning set for determining the geographic position of the exploration system with respect to that of each of the acquisition devices in the field. The central station may comprise equipment making it possible to pick up the hertzian signals transmitted by a geographic positioning system such as the GPS system and it is provided with equipment making it possible to determine the absolute position thereof in space. Acquisition devices in the field comprise equipment sufficient for detecting signals indicative of the relative positioning thereof with respect to the central station. The received signals preprocessed in each acquisition device are transmitted to the central station and combined with those received there for determining the positioning thereof in the field.